Description of Prior Art
Today's airport terminal operations are complex and varied from airport to airport. Airports today are, in many cases, the limiting factor in aviation system capacity. Each airport has a unique set of capacity limiting factors which may include; limited tarmac, runways, suitable approaches, navigational or/and Air Traffic Control (ATC) facilities
Furthermore, operational requirements in the terminal area involve all facets of aviation, communication, navigation and surveillance. The satisfaction of these requirements with technological/potential solutions should be based upon three underlying principles; improved safety, improved capacity and cost effectiveness.
Today airport air traffic control procedures and general airport aviation operations are based on procedures from the 1950's. These air traffic control procedures were initially developed to separate aircraft while in the air. The initial separation surveillance system was a radar system consisting of a rotating radar antenna. The antenna rotated typically about once every 4.8 seconds while transmitting a signal, another receiving antenna picks up a reflected signal from a target. The surveillance system then calculated a range (based on transit time) and an azimuth angle based on the physical orientation of the antenna. The 2-dimensional position was then usually plotted on a display with other detected targets, objects and clutter. Radar today relies on faster rotating antennas or electronically scanned antennas to provide more frequent updates and higher resolution. To further enhance the performance of the target returns, provide altitude information and an identifier, a transponder is used on the aircraft. The transponder is the key element in radar surveillance systems, since without it no identification and no altitude information is provided to the air traffic control system.
Surveillance data from multiple surveillance systems (radars) is then discretely mosaiced or "tiled" into a semi-continuous system. Controllers today separate traffic visually by the rule of "green in between" the target tracks. This is a highly manual method for separation of aircraft, placing stress on the controllers and limits any true automation assistance for the controller.
In the high density and high precision airport environment numerous single function airport systems have been developed over the years to support air traffic control and pilot needs. Precise landing navigation is currently provided by the Instrument Landing System (ILS), while airside navigation is provided by VOR/DME, LORAN and NDB's. Airport air traffic controller surveillance is provided thorough visual means, airport surface detection radar (ASDE), secondary surveillance radar, parallel runway monitoring radar and in some cases primary radar. Each of these systems is single function, local in nature and operation and provides accuracy which is a function of distance to the object being tracked. Merging these navigation and surveillance systems into a 4-dimensional seamless airport environment is technically difficult and expensive. MIT Lincoln Laboratories is attempting to provide an improved radar based Air Traffic Control environment and has received three U.S. Pat. Nos. 5,374,932, 5,519,618 and 5,570,095 reflecting those efforts. These patents relate to improvements of the current localized surveillance and navigation airport environment without the use of GNSS compatible seamless techniques as
These localized systems have served the aviation system well for nearly 50 years and numerous mishaps have been prevented over this period through their use. With the advent of new multi-function technologies superior performance is available at a fraction of the cost of today's current single function systems. The technologies of Global Navigation Satellite Systems, digital communication and low cost commercial computers can support seamless 4-dimensional airport operations at smaller airports unable to justify the heavy financial investment in today's single function navigation and surveillance systems.
Others are also demonstrating and developing similar systems. Haken Lans (GP&C) of Sweden is demonstrating the use of Differential GPS with Self Organizing Time Division Multiple Access datalink communications. The invention of Haken Lans is described in World Intellectual Property Organization document #93/01576. The invention of Fraughton describes an airborne system for collision avoidance in U.S. Pat. No. 5,153,836. The inventions of Lans and Fraughton fail to provide the seamless 4 dimensional GNSS compatible operational and processing environment of Pilley.